MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 1207 PM EDT MON AUG 08 2016 VALID AUG 08/1200 UTC THRU AUG 12/0000 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... 12Z MODEL EVALUATION INCLUDING PREFERENCE AND FORECAST CONFIDENCE ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ STAGNANT/PERSISTENT UPPER CIRCULATION ACROSS THE NERN GULF OF MEX ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: 12Z GFS/00Z ECMWF BLEND CONFIDENCE: SLIGHTLY BELOW AVERAGE THE 00Z UKMET IS A CLEAR OUTLIER RESOLVING A VERY STRONG/CONCENTRIC SOLUTION AS EARLY AS TUESDAY...MAKING IT VERY SUSPECT. THE 12Z NAM CONTINUES TO SUPPRESS THE SUBTROPICAL RIDGING ACROSS THE CAROLINAS INTO THE OHIO/UPPER TN RIVER VALLEYS WHICH ALLOWS THE NAM SOLUTION TO LIFT/SHEAR UPPER LEVEL ENERGY INTO THE WESTERLIES A BIT MORE AGGRESSIVELY THAN THE REST OF THE MODEL SUITE...INCLUDING THE OVER-COOKED UKMET; SUGGESTING RIDGING TO SUPPORT MORE WESTERLY MOTION TO THE OVERALL TUTT. THE 12Z CMC OPPOSED TO THE UKMET...SUPPORTS A STRONGER RIDGE STRENGTH EVEN COMPARED TO THE MORE MODERATE GFS/ECMWF SOLUTIONS...THOUGH WITH WEAKER FLOW ALSO STALLS AND LIFTS NORTH BY DAY 3 MORE ON PAR WITH THE LESSER FAVORED NAM/UKMET TRACKS. THE 12Z GFS CONTINUED A WEAKER TREND EVEN SUPPORTING THE 594DM RIDGE TO ENCOMPASS IT BY THURS...WHICH STILL SEEMS TO BE A BIT TOO WEAK WHILE THE 00Z ECMWF RESOLVES A STRONGER WAVE. IT DOES SEEM PLAUSIBLE GIVEN THE AVAILABLE ENERGY FOR UPSCALE CONVECTIVE GROWTH TO BE SOMEWHERE BETWEEN THESE TWO SOLUTIONS. GIVEN THE LARGER SPREAD AND IMPORTANCE OF CONVECTION...CONFIDENCE REMAINS SLIGHTLY BELOW AVERAGE IN A BLEND OF THE 12Z GFS AND 00Z ECMWF TO REPRESENT THE OVERALL ENSEMBLE SUITE. PLEASE REFER TO THE QPFPFD FOR DETAILS CONCERNING THE PREFERRED GUIDANCE FOR QPF. SHORTWAVE TRACKING ACROSS SRN CANADA MON/TUE WITH COLD FRONT MOVING THROUGH THE GREAT LAKES TUE/WED INTO NEW ENGLAND WED/THUR ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~ PREFERENCE: NON-NAM BLEND CONFIDENCE: AVERAGE WV LOOP SHOWS A SHORTWAVE ACROSS MT INTO SOUTHERN CANADA WITH ASSOCIATED SURFACE LOW TRACKING ACROSS THE NORTHERN TIER/S CANADA TODAY INTO TUES EVENTUALLY SHEARING INTO THE LINGERING TROF AND FRONTAL ZONE LEFT ACROSS CENTRAL CANADA BY THE STRONGER DEEP HUDSON BAY CYCLONE. THE 00Z NAM IS A BIT MORE WOUND UP ALOFT AND THEREFORE SLOWER CROSSING ONTARIO BY TUES/WED BUT DOES NOT SEEM TO NEGATIVELY AFFECT THE TIMING/PLACEMENT OF THE FRONTAL ZONE WHICH IS FAIRLY WELL AGREED UPON THROUGH MUCH OF THE PERIOD. ANOTHER ISSUE WITH THE 12Z NAM IS HANDLING THE SHORTWAVE ACROSS THE MID-MS VALLEY CURRENTLY AND SHIFTING IT ACROSS INTO NEW ENGLAND; SEE SECTION ABOVE...BUT THE WAVE IS MUCH TOO STRONG/WOUND UP COMPARATIVELY SPEAKING LIKELY DUE TO A WEAKER SUBTROPICAL RIDGE. THOUGH THE MASS FIELDS SEEM WELL AGREED UPON...THESE WAVE ISSUES CAUSE ENOUGH DISPARITY TO SUPPORT A NON-NAM BLEND AT AVERAGE CONFIDENCE. PLEASE SEE THE QPFPFD FOR DETAILS CONCERNING THE PREFERRED GUIDANCE FOR QPF CLOSED LOW OVER THE PACIFIC NORTHWEST WITH POSITIVE TILT TROF INTO SOUTHWEST AS WELL AS SURFACE LOW OUT OF NORTHERN HIGH PLAINS TUES/WED. ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~ PREFERENCE: NON-UKMET BLEND CONFIDENCE: AVERAGE WV LOOP SHOWS WELL DEFINED CONCENTRIC CLOSED LOW ALONG THE WA COAST AT THIS TIME...THIS FEATURE SLOWLY ROLLS EAST INTO THE NORTHERN US ROCKIES BY WED WITH UPSTREAM SHORTWAVE ENERGY DIGGING AND CARVING OUT A POSITIVE TILT TROF ACROSS THE MAJORITY OF THE WEST BY WED. THIS PATTERN WILL ALSO BEGIN TO DRAW SHEARED ENERGY FROM TROPICAL CYCLONE JAVIER NORTHEAST ACROSS THE FOUR CORNERS/CENTRAL ROCKIES AND NORTHERN PLAINS BY THURS. OVERALL THE 00Z UKMET SEEMS MOST OUT OF PHASE WITH THE REST OF THE GUIDANCE...SIGNIFICANTLY DEEPENING THE ENERGY OUT OF THE TROPICS FASTER...WHICH IN TURN SLOWS THE EASTWARD ADVANCEMENT OF THE MAIN CLOSED UPPER LOW FEATURE. THE 12Z NAM DID TREND A BIT STRONGER WITH THE WAVE ON THURS IN THE GREAT PLAINS TOO BUT SEEMS ON PAR IN TIMING WITH THE 00Z CMC/12Z GFS AND IS ONLY SLIGHTLY STRONGER A IN THE MID-LEVEL TROF STRENGTH. THE 00Z ECMWF IS UNCHARACTERISTICALLY FASTEST WITH THE CENTER OF THE CLOSED LOW BY THURS IN S CANADA AND DEEPER BUT STILL MATCHES WELL WITH THE SHAPE TO THE NON-UKMET SUITE...PARTICULARLY GIVEN THE MODERATE TO SMALL SPREAD FOR DAY 3. AS SUCH WILL KEEP A NON-UKMET BLEND AT AVERAGE CONFIDENCE GIVEN THE VARIABILITY OF THE SMALLER SCALE FEATURES (MAINLY EJECTING OUT OF THE SOUTHWEST). SINCE YESTERDAY...THE CMC HAS TRENDED FASTER TOWARD THE CONSISTENT ECMWF...AND THE GFS HAS TRENDED A BIT SLOWER TOWARD THE ECMWF. GIVEN THE GROWING CONSENSUS...THE 00Z GFS AND 00Z ECMWF APPEAR TO BE THE BEST COMPROMISE FOR THIS SYSTEM...FOLLOWED CLOSELY BY THE 00Z NAM AND 00Z CMC...DESPITE SOME MINOR WOBBLES IN POSITION FROM RUN TO RUN. THE 00Z UKMET LAGS SIGNIFICANTLY BEHIND THE DETERMINISTIC/ENSEMBLE CLUSTERING. GALLINA www.wpc.ncep.noaa.gov/html/model2.shtml... www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml...